Github user uce commented on the pull request:
https://github.com/apache/incubator-flink/pull/63#issuecomment-54751876
Thanks for the review. The initial value for the reduce function and the
count operator are tightly connected. The reduce with initial value is the
general solution, of which the count operator is a special case. Therefore, I
wouldn't say that these are independent features. The refactorings are also
limited to files related to the initial value reduce/count operator.
The counting for grouped data sets was a quick fix after @hsaputra's
comment. We can either fix it with this PR or open a seperate issue if we want
to merge it.
I think the limitation to AllReduce was the result of a discussion with you
and @StephanEwen.
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All in all, I think that we should wait for the upcoming changes to the
runtime and scheduler to support the more intuitive API of simply returning the
count to the user program. As you said, we might move some of the changes (like
initial value reduce) to a separate issue if we find them useful.
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